Radio goniometers and radio direction finders incorporating the same



July 18, 1967 .J. F. HATCH 3,332,082

RADIO GONIOMETERS AND RADIO DIRECTION FINDERS INCORPORATING THE SAME 2Sheets-Sheet 1 Filed May 5, 1965 CRT July 18, 1967 J F HATCH 3,332,082

RADIO GONIOME'iER S AND RADIO DIRECTION FINDERS INCORPORATING THE SAMEFiled May 5, 1965 2 Sheets-Sheet ATTORNEYS United States Patent Ofi3,332,082 Patented July 18, 1967 ice 3,332,082 RADIO GONIOMETERS ANDRADIO DIRECTION FINDERS INCORPORATING THE SAME James Frederick Hatch,Hutton, England, assignor to The Marconi Company Limited, London,England, a compauy of Great Britain Filed May 5, 1965, Ser. No. 453,388Claims priority, application Great Britain, May 13, 1964, 20,007/ 64 1Claim. (Cl. 343-124) ABSTRACT OF THE DISCLOSURE A radio goniometer foruse in radio direction finders which comprises inner and outerrelatively rotatable coaxial members. The outer member has wound thereonseveral equally spaced windings and the inner member has wound thereontwo similar windings at right angles one to another. The inner and outermember windings are wound with the turns thereof progressing first inone direction and subsequently in another direction such that the turnsin any one winding are effectively in parallel planes. Each inner memberwinding consists of two parallel connected winding parts, one on eachside of a center line.

The two inner member windings supply input signals to the two paths of atwin-path receiver of a radio direction finder.

The outer member winding may have a common central point capable ofproviding input signals to one of the paths of the twin-path receiverfor sense determination.

Alternatively, the outer windings may have separate central points. Inthis case the central point of the winding associated with an aerialwhich is most nearly at right angles to the incoming signal is connectedto one path of the twin-path receiver for sense determination.

This invention relates to improvements in or modifications of radiogoniometers and radio direction finders incorporating the same and moreparticularly, although not exclusively, to such goniometers anddirection finders intended for operation in the high frequency (H.F.)waveband extending between the approximate limits of 2 mc./s. and 30mc./s.

Radio goniometers of the type to be modified and improved by the presentinvention are disclosed in British Patent No. 944,861, the main objectof which was to satisfy a requirement for a goniometer having more thantwo stator coils-a requirement which had previously been regarded asvery difficult to satisfy both because of the danger of undesirablecoupling between coils which are not perpendicular to one another andthe difficulty, in a goniometer which is physically sufiiciently smallto operate satisfactorily at the highest frequency in question, ofproviding adequate efficiency of signal transfer between the stator androtor coils.

According to the aforementioned British patent a radio goniometercomprises two coaxial relatively rotatable members, one within theother, the outer member being formed of a ring-like ferrite body with atleast three windings equally spaced around the ring and wound round thesection thereof, each winding comprising two diametrically oppositehalf-windings arranged to produce opposing magnetic fluxes in said bodyand the inner member being provided with a winding for magneticallycoupling in turn, during rotation, with each of said windings on theouter member. The various subordinate features of invention claimed inthe above British patent include providing the inner member with awinding which progresses initially in one direction and subsequently inthe opposite direction whereby all the turns thereof are effectively inparallel planes also providing the outer member with a winding whichprogresses initially in one direction and subsequently in the oppositedirection whereby all the turns thereof are effectively in parallelplanes; making the inner member with two winding parts, one on each sideof the centre line, connected in parallel each winding part progressinginitially in one direction and subsequently in the opposite directionwhereby all the turns thereof are effectively in parallel planes andconstituting the outer member by a stator of cylindrical form havingfour winding parts.

The particular description contained in the aforementioned Britishpatent, however, describes only radio goniometers having but one rotorwinding. Such a radio goniometer is of course adapted to provide signalsto a single channel receiver. There are, however, twin-path receivers,each path containing an amplifier substantially identical with that inthe other, which can be most advantageously employed in conjunction witha multi-aerial system consisting of a number of aerials spaced around acircle, to indicate directly on a cathode ray tube on incoming signaldirection. A single radio goniometer as particularly described in theaforementioned British patent is obvious- 1y not suitable for supplyingsignals from the aerial system to the twin-path receiver since saidreceiver requires two inputs, one to each path. The present inventionseeks to improve or modify radio goniometers as set forth in the saidBritish patent in such manner as to make a single improved or modifiedgoniometer suitable for supplying both input signals to the twin-pathreceiver.

According to this invention the inner member of a radio goniometer asclaimed in the above-mentioned British patent is provided with twosimilar windings substantially at right angles to one another and eachof Which provides, during rotation, magnetic coupling With each of thewindings in the outer member in turn.

The outer member of a radio goniometer in accordance with this inventionand/or the windings provided thereon may take any of the forms describedor claimed in the aforementioned British patent and similarly, each ofthe mutually perpendicular windings on the inner member may take any ofthe forms described or claimed in the said British patent.

The invention is further described with reference to the accompanyingdrawings. In the drawings FIGURES l and 2 are diagrammaticrepresentations of the stator, and FIGURES 3 and 4 are diagrammaticrepresentations of the rotor, of a radio goniometer in accordance withthis invention; FIGURE 5 shows diagrammatically a twinpath directionfinder incorporating the goniometer of FIGURES 1, 2, 3 and 4; and FIGURE6 shows an improved and preferred twin-path direction finderincorporating a goniometer in accordance with this invention.

Referring to FIGURE 1, the goniometer stator comprises a ring-likeferrite body P8 of cylindrical form carrying four windings wound aroundits section. Each winding is comprised of two half windings and thereare therefore, as illustrated, eight similar half windings symmetricallydisposed on the ferrite cylinder. Each winding is made up of twodiametrically opposed half windings whereby one winding is constitutedby half windings 1 and 1 another by the half windings 2 and 2 a third byhalf windings 3 and 3 and a fourth by half windings 4 and 4 The spacingof the turns of each winding and the spacing between adjacent windingsare preferably arranged to be equal, as shown, so that adjacent turns,Whether on the same winding or on different windings, are equally spacedfrom one another. In the illustrated example each half winding iscomprised of eight turns each embracing 5 of arc.

The interconnections between the half windings on the stator arerepresented in FIGURE 2 in which, for simplicity, only two halfwindings, together constituting a single stator winding, are shown. Itwill be seen from FIGURE 2 that the two half windings illustrated aresimilar windings and that they are inter-connected in such manner thatthe magnetic fluxes in the ferrite cylinder FS, resulting from theapplication of a potential between the winding terminals T1 and T2,oppose one another whereby a concentrated magnetic field extendsdiametrical ly across the cylinder FS.

Conveniently the windings may be so arranged that connections may bemade to two of them, for example windings 11 and 3-3 at one end of thecylinder FS and connections made to the other two, for example 2-2 and44 at the other end.

The goniometer rotor illustrated in FIGURES 3 and 4 comprise a hollowcylinder IR of ferrite material carrying thereon two similar windings W1and W2 which are at right angles to one another and are shown purelyschematically in FIGURE 3. Each of these windings consists of twosymmetrically arranged coils, 1W1, 2W1 and 1W2, 2W2 respectively, eachof which is wound in the manner described in the previously mentionedBritish patent and illustrated by FIGURE 3 thereof. FIGURE 4 of thepresent specification is, except for the references, identical withFIGURE 3 of the said British patent and shows the manner in which eachcoil is wound. In order not to complicate the accompanying FIGURE 4 onlyone coil is shown. This is referenced 1W1 to indicate that it forms halfof the winding W1. There are three more similar coils of which one (2W1,FIGURE 3) is parallel to 1W1 and is connected electrically in paralleltherewith and the other two (1W2, 2W2, FIGURE 3) are parallel to oneanother, connected electrically in parallel with one another and are atright angles to 1W1. As will be seen from FIGURE 4 the turns of 1W1 lieapproximately parallel to one another and progress towards the leftacross substantially half the rotor (in the figure) for the desirednumber of turns and then back again towards the right (in the figure)for the same number of turns. As a result those parts of the coil whichhave a component in the direction of progression cancel one another outso that all the turns of the coil lie effectively parallel to oneanother.

The goniometer is of course provided with central spindles mounted inbearings and when completely assembled the rotor is coaxially within thestator with the rotor windings coupling in turn, during rotation, withthe different stator windings. Out ut signals from the rotor windingsmay conveniently be taken off from the rotor by means of sliprings (notshown).

FIGURE 5 represents a direction finder incorporating a radio goniometeras above described for operation over a continuous frequency band of 2mc./s.30 mc./s. Referring to FIGURE 5 there are eight linear verticalaerials A1, A2, A3, A4, A1 A2 A3 and A4 symmetrically disposed around acircle having a diameter of approximately at a frequency of 25 mc./s.The aerials are unbalanced uni-pole aerials and are mounted on theground or on a simulated earth plane and have their bases insulatedtherefrom. The members of each pair of diametrically opposite aerialsare connected via coaxial cables to respective ends of an appropriatestator winding of a goniometer as illustrated by FIGURES 1 to 4. Thestator windings are indicated diagrammatically in FIGURE 1 at 1, 1 2, 23, 3 and 4, 4 aerials A1 and A1 being connected to the half windings 1,1 aerials A2 and A2 being connected to the half windings 2, 2 and so on.The half windings are connected to a common point which is taken asshown to one contact of a two-position two armed switch S1. One windingW1 on the rotor is connected to two other contacts of the switch S1 asshown the remaining contact of which is earthed and the arms of whichare connected to the input terminals of one amplifying channel C1 of atwin=path receiver. The other winding W2 on the rotor similarly feedsinto the other amplifying channel C2 of the receiver. The output fromthe channel C1, normally an intermediate frequency (I.F.) output, is fedto the two arms of a second switch S2 which may be ganged with theswitch S1 and which, when in the position shown, supplies the IF.signals via an amplifier IFI to one of the two co-ordinate deflectionsystems of a display cathode ray tube CRT. I.F. output from C2 isamplified by a similar I.F. amplifier I.F.2 fed to the other deflectionsystem of the tube.

With the switches S1 and S2 in the positions shown the goniometer rotorcan be set to a fixed position (say and bearings of incoming signalswill be displayed directly by the cathode ray tube which will produce,from an incoming signal, a straight trace as indicated at T thedirection of which is representative of the incoming signal direction,the tube face being provide with a suitable scale against whichindicator directions can be read. If the goniometer rotor is rotated,the trace will rotate in the opposite direction and, at the positoin ofthe figureofeight minimum, the trace will set always in the NS. or E.W.direction, depending on which search coil is in use, irrespective of theincoming signal direction. It is convenient to arrange this direction tobe horizontal on the tube face. Therefore if, at any time, the signal isfading and phase interference effects cause an indicated signaldirection to wander, the goniometer rotor can be rotated to thatposition which gives the best average position about the horizontal onthe tube face. When the signal amplitude is at a maximum an improvedindicated bearing is usually obtained and this condition can be obtainedby observing the tube while turning the rotor to the best position. Apointer P on the rotor shaft reads on a suitable scale as to indicatethe position of the rotor.

Aerial monitoring of the signal can readily be done as well (this is notillustrated) by switching headphones to receive signals from the channelwhich is set to the figureof-eight maximum while swing bearings aretaken on the horizontal tube trace fed from the other channel which,being energised from the other rotor winding, will carry a minimumsignal at this time.

Sense of a bearing is obtained by pulling the switches S1, S2 to theirother positions. As the tube shows a horizontal trace when thegoniometer is set to the figure-ofeight minimum, the channel feeding thevertical deflection system of the tube is available for brilliancemodulation of the tube in one direction or the other to indicate rightor wrong sense, as the case may be. In the arrangement of FIGURE 4 thisis done, when switches S1 and S2 are in their up positions by takingoutput from the common point of the stator coils to channel C1 andtaking the output from this channel via a 90 phase shifter PS andamplifier P.S.A. to the control grid of the tube.

FIGURE 6 illustrates an improved direction finder which, in generalprinciple, resembles that in FIGURE 5 but which uses a preferred methodof effecting sense determination. Like references are used for likeparts in FIGURES 5 and 6. FIGURE 6 is shown only so far as is necessaryto an understanding of the way in which it differs from FIGURE 5, partsnot shown in FIGURE 6 being as in FIGURE 5.

In FIGURE 5 the centre points of all the stator windings 1, 1 2, 2 3, 3and 4, 4 are connected together and the common point used, when sensefinding, to provide a source of vertical This, of course, involves areduction in sense signal amplitude which occurs at .766 when all thecentre points are connected together. The improved arrangement of FIGURE6 avoids this defect. In FIGURE 6 the centre point between each pair ofstator windings 1, 1 2, 2 3, 3 4, 4 is brought out separately and aselector switch is employed to select, as a source of vertical E.M.F.for sense determination, the centre point between the stator windingsconnected to that pair of aerials which, at the moment considered, ismost nearly at right angles to the incoming signal direction. Theselector switch is driven with the rotor of the goniometer and, in theparticular arrangement of FIGURE 6, is constituted by a commentatorswitch CS which, as the rotor rotates, chooses the relay coils RL1, RL2,RL3, RL4 in turn for energisation when the sense switch SW is closed.Each relay coil operates a relay switch RS1, RS2, RS3 or RS4 and, aswill be apparent from 6, these select the centre points of the statorwindings 1, 1 2, 2 3, 3 4, 4 in turn for use to provide the requiredvertical E.M.F. for sense determination.

I claim:

A direction finder comprising a twin path receiver, a radio goniometerhaving an inner member and an outer member, said outer member having atleast two spaced windings, said inner member having two similarwinding-s substantially at right-angles to one another each of which twosimilar windings provides during rotation magnetic coupling with each ofthe windings of the outer member in turn, said two similar windings ofthe inner member being connected to supply input signals respectively tothe two paths of said receiver, means for connecting each of the ends ofeach of the windings on said outer member to a different one of aplurality of pairs of aerials and each of the windings of the outermember 25 having a separate central point, selection means responsive tothe position of said inner member of the radio goniometer for takingsignals from the central point of A the outer member winding connectedto the pair of aerials which lie on a line which is most nearly at rightangles to the incoming signal direction, and switching means fordisconnecting one of said two inner member windings from one path of thereceiver and for applying the signal taken by the selection means tosaid one path of the receiver for sense determination.

References Cited UNITED STATES PATENTS 1,955,267 4/1934 Woods 343-1152,305,257 12/1942 James et al 343124 2,479,586 8/1949 Moore et a1.343124 2,815,506 12/1957 Tanaka et a1. 343-124 2,885,672 5/1959 Baur343124 FOREIGN PATENTS 894,379 12/ 1944 France.

972,233 6/ 1959 Germany.

773,235 4/ 1957 Great Britain.

944,861 12/1963 Great Britain.

RODNEY D. BENNETT, Primary Examiner. CHESTER L. JUSTUS, Examiner. D. C.KAUFMAN, Assistant Examiner.

